1. Field of the Invention
This invention relates to an air cushion with projections. The projections are bonded to the cushion with an ultra-sonic heat bonder.
2. Discussion of the Related Art
The applicant has already designed and commercialized an air cushion made of conventional PVC sheet. It too has projections made of chlorinated vinyl resin bonded to it using the same ultrasonic heat method. The former cushion supports one's back firmly, and its hemispherical projections effectively improve the blood-circulation and relieve muscular fatigue. However, since the main body of the cushion was made of conventional PVC sheet, its surface was uncomfortably sticky to the touch and needed to be covered, with a lace or cotton cover. As a result, the combined price of both the original cushion along with the required cover was high, while many users also felt that the unit was heavy and carrying it was an inconvenience.